None.
The present invention relates to the art of printing onto rollfeed media and, more particularly, to a media roll support spindle and brake mechanism which reliably governs tensioning of the media. One prior art example of rollfeed spindle and braking device for rollfeed media is disclosed in published European Patent Publication 0 905 072 owned by the assignee of the present invention. Since the rollfeed media should be pulled from the roll with a substantially constant or at least a controllable amount of tension, a spindle brake which uses a stainless steel brake drum engageable with a spring biased pivotally mounted brake shoe has been employed for this purpose. It has been noticed that undesired alteration of the designed amount of back tensioning of the media frequently results from repeated handling of the spindle assembly. This has now been determined to be the result of finger contact with the cylindrical surface of the brake drum which often takes place as the media support spindle is removed from the printer cabinet to replace a media roll leaving fingerprint oil or grease or other contamination on the surface of the metal brake drum which alters the coefficient of friction and hence the tension of the media roll.
It is accordingly the objective of the present invention to overcome this problem and achieve relatively constant tensioning of the rollfeed media.
The present invention therefore provides a rollfeed media tensioning system for a printer, said system comprising a rotary media roll support spindle which includes a brake drum and a spindle brake mechanism including at least one brake surface for braking rotation of said spindle, said system further comprising a friction ring mounted on said brake drum and positioned for engagement by said brake surface to urge said friction ring into engagement with said brake drum to brake rotation of said spindle.
The present invention further provides a printer including a support for a supply of rollfeed media to be pulled from said roll to a station at which printing on said media takes place and a rollfeed media tensioning system comprising a rotary media support spindle which includes a brake drum and a spindle brake mechanism, said spindle brake mechanism including a friction ring mounted on said brake drum, and at least one contact surface engaging said friction ring with a predictable amount of force to urge said friction ring into frictional engagement with said brake drum to brake rotation of said spindle.